Pyrolysis of vinylacetylene between 300 and 450°C

✍ Scribed by Richard Lundgard; Julian Heicklen

• Publisher: John Wiley and Sons
• Year: 1984
• Tongue: English
• Weight: 1014 KB
• Volume: 16
• Category: Article
• ISSN: 0538-8066
• DOI: 10.1002/kin.550160205

✦ Synopsis

Vinylacetylene was pyrolyzed at 300-450°C in a packed and an unpacked static reactor with a pinhole bleed to a quadrupole mass spectrometer. The reactant and C,H, products were monitored continuously during a reaction by mass spectrometry. In some runs, the products were also analyzed by gas chromatography after the run. In these runs CH,, C2H6, C3H6, and C2H, were also detected.

The reaction for vinylacetylene removal and C,H, formation is homogeneous, second order in reactant, and independent of the presence of a large excess of N, or He. However, C,H, formation is about half-suppressed by the addition of the free-radical scavengers NO or 0,. The rate coefficient for total vinylacetylene removal is 1.7 x lo6 exp(-79 2 13 kJ/mol RT) L/mol . s. The major reaction for C,H, removal is polymerization. In addition four C,H, isomers, carbon, and small hydrocarbons are formed. The three major C,H, isomers are styrene, cyclooctatetraene (COT), and 1,5dihydropentalene (DHP).

The C,H, compounds are formed by both molecular and free-radical processes in a second-order process with an overall k = 3 x 10' exp( -122 kJ/mol R T ) L/mol . s (average of packed and unpacked cell results). The molecular process occurs with an overall k = 8.5 x lo7 exp ( -118 kJ/mol RT) L/mol . s. The COT, DHP, and an unidentified isomer (d), are formed exclusively in molecular processes with respective rate coefficients of 4.4 x lo4 exp( -77 kJ/mol RT), 1.7 x lo5 exp(G89 kJ/mol RT), and 3.1 x lo9 exp(-148 kJ/mol RT) L/mol . s. The styrene is formed both by a direct free-radical process and by isomerization of COT.